The following description is provided to assist the understanding of the reader. None of the information provided is admitted to be prior art.
In data storage architectures, a client's data may be stored in a volume. A unit of data, for example a file (or object), is comprised of one or more storage units (e.g. bytes) and can be stored and retrieved from a storage medium such as disk or RAM in a variety of fashions. For example, disk drives in storage systems are divided into logical blocks that are addressed using logical block addresses (LBAs). As another example, an entire file can be stored in a contiguous range of addresses on the storage medium and be accessed given the offset and length of the file. Most modern file systems store files by dividing them into blocks or extents of a fixed size, storing each block in a contiguous section of the storage medium, and then maintaining a list or tree of the blocks that correspond to each file. Some storage systems, such as write-anywhere file layout (WAFL), logical volume manager (LVM), or new technology file system (NTFS), allow multiple objects to refer to the same blocks, typically through a tree structure, to allow for efficient storage of previous versions or “snapshots” of the file system. In some cases, data for a single file or object may be distributed between multiple storage devices, either by a mechanism like RAID which combines several smaller storage media into one larger virtual device, or through a distributed storage system such as Lustre, General Parallel File System, or GlusterFS.
During operation, volumes of data may be moved between various clusters. For example, a volume may be moved for performance or other maintenance purposes. Additionally, new volumes of data may be added or imported to a storage system. However, the most efficient cluster on which to move an existing volume or on which to import a new volume needs to be determined by a system administrator.